PROJECT SUMMARY
Ischemia-reperfusion (IR) injury is a significant challenge in treating myocardial infarction (MI), the leading
cause of death in the United States. Mitochondrial reactive oxygen species (mtROS) generated by electron
transport chain (ETC) Complex-I are the principal mediators of IR injury. Excess mtROS generated during
early IR triggers vicious cycles of free radical production promoting cardiomyocyte death. Therefore,
understanding the early molecular events of reperfusion will provide new targets for developing novel
interventions for limiting cardiac injury. Our published findings show that LonP1- a major mitochondrial stress
response protease mitigates oxidative stress-induced damage during early IR; therefore, LonP1 could be a
promising target for attenuating reperfusion injury. Our long-term goal is to leverage the mitochondrial protein
quality control mechanisms of LonP1 as a pivotal point to develop therapeutic strategies for mitigating IR injury
and post MI- heart failure. Our published findings show that increased LonP1 expression in the heart induced
by ischemic preconditioning (IPC) or transgenic overexpression (LonTg) reduced IR injury and favors
cardioprotection. Whereas, LonP1 downregulation (LONP1+/-) abrogated IPC-mediated cardioprotection.
Importantly, LonTg hearts showed reduced levels of Complex-I subunits (but not Complex II-V subunit) and
oxidative damage during early IR (within 30 min reperfusion) compared to NTg controls. Conversely, our
additional findings show that LonP1 downregulation in cardiomyocytes upregulated Complex-I activity,
increased superoxide levels, and showed early reperfusion-induced cell death activation. In addition, we have
identified a small molecule activator of LonP1 that significantly reduced hypoxia-reoxygenation (H/R) induced
myocyte death in a dose-dependent manner in vitro. With additional data on IR-induced acetylation of
Complex-I matrix subunits and LonP1 dependent Complex-I remodeling during IR, we hypothesize that LonP1
mitigates myocardial injury by suppressing excess mtROS generation through tight regulation of Complex-I
during early IR. We will test our hypothesis by the following specific aims: Aim 1 will delineate the
mechanism(s) by which LonP1 modulates Complex-I levels, activity and reduces oxidative stress during IR.
Aim 2 will test that LonP1 remodels Complex-I and its associated supercomplexes by degrading IR-induced
post-translationally modified (PTM) Complex-I matrix subunits, thereby reduce mtROS during early IR. Aim 3
will determine the therapeutic potential of LonP1 activators in treating myocardial IR injury in vivo. By
determining the molecular mechanisms of LonP1-mediated cardioprotection and the therapeutic potential of
LonP1 activators, we will define the role of LonP1 in cardioprotection and develop novel therapeutic tools and
strategies to mitigate IR injury.